1. Field of the Invention
The present invention relates to vacuum furnaces and, more particularly, to the arrangement of electrical heating elements in such a furnace.
2. Description of the Related Art
Conventionally, electrical heating elements are disposed in such furnaces closely adjacent to the walls of the furnace, the elements comprising either sinuously wound elongate resistive elements, or pad-like sintered resistive elements arranged around the inner periphery of the furnace. Vacuum furnaces have a pressure vessel inside which are arranged insulating elements to minimise heat transfer to the walls of the pressure vessel in order to protect the integrity of the vacuum under which the vessel operates in use.
However, when there are multiple workpieces being treated in the furnace, unless they are all positioned equidistantly from the heating elements, non-uniform heat treatment of the load may occur. Furthermore, masking of the radiated heat applied to particular workpieces can also occur, resulting in insufficient heat treatment thereof.
Additionally, the application of differential heating to certain types of workpieces is difficult to achieve in a satisfactory manner.